JPH105090A - Clouding-proof mirror - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of bedew and to avoid heat crack by additionally providing a planar heat generator on the rear side of a mirror and suppressing thermal stress, which is generated at the edge part of glass plate, less than specified by specifying the capacitance of the heat generator corresponding to the unit area of the mirror. SOLUTION: The rapid heating of the mirror is avoided and always or excepting for sleeping at least, the mirror is set at the temperature higher than the room temperature for several deg.C or less than 10 deg.C for a long time. Besides, the planar heat generator is additionally provided on the rear face of the mirror and this planar heat generator is adopted with the design of capacitance less than 120W/m<2> and more than 30W/m<2> . Otherwise, when adopting the planar heat generator of much higher output, it is enough only to previously set the capacitance less than 120W/m through an output control mechanism and in case of use, the planar heat generator is always electrified or the electrification is stopped only during sleeping by switch operation. As a result, the generation of bedew can be prevented, sharp reflected images can be always watched, thermal stress at the terminal edge part of the mirror can be suppressed less than 55kg/cm<2> as well and the generation of heat crack can be practically eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mirror for use in bathrooms, vanities, and the like. In order to prevent the occurrence of dew condensation on the mirror surface during use, a so-called surface heating element is provided on the back of the mirror. The present invention relates to an anti-fog mirror and its use.

[0002]

2. Description of the Related Art It is already known to arrange a surface heating element on the back surface of a mirror in order to prevent dew condensation on the surface of the mirror.

Japanese Utility Model Publication No. 51-38456 discloses an electric heating type anti-fog mirror in which a panel heater is provided on the back of the mirror and a thermostat is further provided on the back, and in particular, the mirror and the panel heater are connected to each other. 1cm width of unheated area around
In addition, Japanese Utility Model Publication No. 51-38458 discloses that the width of the non-heated area around the mirror and the panel heater is set to 5 cm or more in a similar electrically heated anti-fog mirror. ing.

[0004] The fracture stress of the mirror, ie, the glass plate, is weaker at the edges than in the plane. For example, in a float glass sheet having a thickness of 5 mm, the average fracture stress in the plane is 500 kg / cm ² , whereas the average fracture stress is 500 kg / cm ² . The average breaking stress is 360 kg / cm ² .

However, when the mirror is heated, thermal stress is generated unless the whole is heated uniformly. However, especially at an edge portion where heating is apt to be delayed, destruction is likely to occur due to the small breaking stress. .

[0006] In the above-mentioned prior art, the purpose is to sufficiently suppress the generation of stress at the edge by sufficiently heating the edge, thereby preventing the destruction of the edge. The object of the present invention is to suppress the generation of thermal stress at the edge and to prevent the edge from being broken by setting the non-heated area up to the edge and the vicinity of the edge inside the edge.

Japanese Utility Model Publication No. 53-16359 discloses that in a glass anti-fog mirror provided with an electric heater on the back surface, the corners of the anti-fog mirror are heated from the center of each periphery (side). Have been. This focuses on the fact that destruction is likely to occur at the center of the side, and by controlling the heating of the part and the vicinity thereof, the generation of stress in the part is suppressed and destruction is prevented.

When a mirror is actually used in a bathroom or the like, a sharp heating is applied in order to quickly remove the dew condensation at the time of use. Often destroyed.

For example, an electric heating type surface heating element which is generally commercially available has a capacity of 200 to 500 W / m ² as shown in Table 2, whereby the surface temperature of the mirror is about 3 to 5 minutes. Reach room temperature + 15-30 ° C, and dew is removed. However, as described above, such rapid heating tends to lead to breakage from the edge. Alternatively, to prevent this, the heat-generating part is usually devised such that it is located closer to the center by 10 cm or more than the edge of the mirror. It will not be used.

The aforementioned Japanese Utility Model Publication No. 51-38458 and Japanese Utility Model Publication No. 53-16
No. 359 has a heat-generating part located near the center as described above, and condensation is removed only at the center of the mirror.Furthermore, as described in Japanese Utility Model Publication No. 51-38456, surface heating is required to heat even the edge. There are many disadvantages and disadvantages, such as the outer dimensions of the body must be larger than the size of the mirror.

An object of the present invention is to provide an anti-fog mirror which solves the above-mentioned problems and inconveniences and does not require cost.

[0012]

SUMMARY OF THE INVENTION The present invention is directed to a mirror having a metal film including a silver mirror film and a backing coating formed on the back surface of a glass plate, wherein a surface heating element is provided on the back surface of the mirror, By setting the body volume to 30 to 120 W / m ² per unit area of the mirror, the thermal stress generated at the edge of the glass plate can be reduced to 55 kg / cm.
^The anti-fog mirror is prepared so as to be ² or less, and is prepared in advance so that the maximum capacity of the surface heating element is 120 W / m ² or less.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In an anti-fog mirror, the center of the mirror is heated by a surface heating element and expands. However, since the edge is almost at room temperature, a thermal stress is generated due to a difference in thermal expansion of glass. Tensile stress usually accompanies the expansion of the central portion at the edge. In other words, when the heater is energized, the state is the same as in the case where the edge bending test is performed. When the generated thermal stress exceeds the edge bending strength of the glass, breakage, that is, thermal cracking occurs.

The average bending fracture stress and allowable stress of the clean-cut float glass used as the base plate for the mirror are shown in Table 1, and the allowable stress at the edge portion under a long-term load condition is a safety factor. It is 70 kg / cm ² at 2.0 (thousandths of the destruction probability).

By the way, in recent years convenience in living space,
There is an increasing tendency to seek comfort, and it is becoming common to attach such heaters to bathroom mirrors and vanity mirrors, but along with that, heat breaks in the mirrors, thereby causing injury to the user And complaints about the
There is also an increasing tendency for mirror maker manufacturers to be responsible for manufacturing due to the enforcement of the so-called P / L law. Looking at an example of a mirror thermal cracking accident, according to the so-called mirror face method of estimating the fracture stress from the radius of the mirror face generated at the starting point of fracture when a glass plate breaks due to thermal stress, 100 kg /
Some of them are about ² cm ² , and the setting of 70 kg / cm ² is not always sufficient as the allowable stress.

The present inventor has conducted intensive studies on this, and
The invention has been completed, i.e., avoid sudden heating of the mirror, always, or at least for a long time except during sleep, set a temperature higher than room temperature by a few degrees Celsius to less than 10 degrees Celsius, Therefore, if the capacity of the surface heating element is set to 30 to 120 W / m ² per unit area, the occurrence of dew condensation can be prevented,
The reflected image is always clear and the thermal stress at the edge of the mirror is 55 kg.
/ Cm ² or less, and substantially no thermal cracking (safety factor 2.6, estimated damage probability 1 / 100,000 or less) An anti-fog mirror can be obtained.

Regarding the power consumption, the conventional case: surface heating element capacity 500 W / m ² (heater size 200 × 300 mm; 30 W per sheet) 1000 W / m ² . ): Surface heating element capacity 40W / m ² (heater size “200 × 300mm. 2.4 W per sheet”) It is 960W / m ² .day when energized constantly. Can be reduced.

That is, a surface heating element is attached to the back surface of the mirror,
The surface heating element has a capacity of 120 W / m ² or less (30
(W / m ² or more), or when using a higher-output surface heating element, the output control mechanism should be set in advance to 120 W / m ² or less. At this time, the surface heating element may be always energized, or may be turned off only during sleep by operating a switch.

[0019]

【Example】

[Mirror surface temperature and generated thermal stress] The following were employed as the test mirror and the electrically heated surface heating element (heater). Mirror; size 330 × 400 × 5 (thickness) mm heater; Dimensions 190 × 340 mm, heating unit dimensions 160 × 310 mm heat - data - capacitance per unit area of a rated power 400W / m ² (per one 20W) Figure 1A is a mirror FIG. 1B is a front view showing the positional relationship between the heater and the heater.
Is a side view of the same, 1 is a mirror, 2 is a heater, 15
Is a heat insulating material adhered to the back of the heater (Styrofoam, 10mm thick), 3 is a spacer, 4 is a support plate (10mm thick plywood), 5 is a column, 6 is a base plate, and the point α is chromel-alumel thermoelectric. A pair is set so that the temperature of the mirror surface is measured, and a strain gauge (KFG-5-120-C1) is provided at a point β.
And the thermal stress on the upper side of the mirror was measured. The output of the heater was changed by changing the applied voltage in various ways with Slidax. The generated thermal stress was measured when the device was in an equilibrium state after 2 hours of energization.

[Anti-fogging test] A glass plate anti-fog performance test apparatus was manufactured in accordance with the provisions of JIS S 4030 "Test method for anti-fog agent for glasses", and a test mirror shown in FIGS. 1A and 1B was set.
In the plan view of FIG.
Consists of a heat insulation box 8 and a cooling device 9, between which a test mirror 10 is mounted, the inside of the box is kept at 30 ° C., and after 2 hours of energization of the heater, steam is jetted out of the humidifier nozzle 11 to start an anti-fog test. The fogging condition was visually observed through a transparent plate 13 provided with a wiper 12. The fogging condition was photographed by the camera 14 and recorded.

[Test Results] As is clear from Table 3, the dew condensation can be prevented by setting the temperature higher than the room temperature by several degrees to less than 10 degrees Celsius at all times, or at least for a long time except during sleep. The reflection image is always clearly seen, the thermal stress at the mirror edge is 55Kg / cm ² or less, and there is virtually no thermal cracking (safety factor 2.6, estimated damage probability 1 / 100,000 or less) ) An anti-fog mirror can be obtained. In addition, there is an effect that the amount of power consumption is not inferior to the conventional case, or that the amount of power consumption can be further reduced depending on the setting.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

[Table 3]

[0025]

According to the present invention, dew condensation can be prevented by avoiding sudden heating of the mirror and setting the temperature to be several to less than 10 ° C. higher than room temperature at all times, or at least for a long time except during sleep. It can prevent the occurrence, the reflected image is always seen clearly, and the thermal stress of the mirror edge is 55Kg / cm2 or less and there is virtually no thermal cracking (safety factor 2.6, estimated damage probability 100,000 min. 1) An anti-fog mirror can be obtained. In addition, there is an effect that the power consumption can be reduced to a level equal to or less than that of the conventional case.

[Brief description of the drawings]

FIG. 1A is a front view showing a positional relationship between a mirror and a heater, and FIG. 1B is a side view of the same.

FIG. 2 is a schematic plan view of a mirror anti-fog performance test apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mirror 2 Heater 7 Mirror (glass plate) Anti-fog performance test device 10 Test mirror α Thermocouple set position β Strain gauge attachment position

Claims (2)

[Claims] 1. A mirror having a metal film including a silver mirror film and a backing coating formed on the back surface of a glass plate, a surface heating element is provided on the back surface of the mirror, and the heating element capacity is reduced to a unit area of the mirror. 30 to 1
An anti-fog mirror characterized by being prepared so that the thermal stress generated at the edge of the glass plate is set to not more than 55 kg / cm ² by setting it to 20 W / m ² . 2. The anti-fogging mirror according to claim 1, wherein the anti-fog mirror is prepared in advance so that the maximum capacity of the surface heating element is 120 W / m ² or less.